Messages in this thread | | | From | Dan Williams <> | Date | Mon, 24 May 2021 17:53:54 -0700 | Subject | Re: [RFC v2-fix-v2 2/2] x86/tdx: Ignore WBINVD instruction for TDX guest |
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On Mon, May 24, 2021 at 5:40 PM Andi Kleen <ak@linux.intel.com> wrote: > > > On 5/24/2021 4:42 PM, Dave Hansen wrote: > > On 5/24/21 4:32 PM, Kuppuswamy Sathyanarayanan wrote: > >> Functionally only DMA devices can notice a side effect from > >> WBINVD's cache flushing. > > This seems to be trying to make some kind of case that the only visible > > effects from WBINVD are for DMA devices. That's flat out wrong. It > > might be arguable that none of the other cases exist in a TDX guest, but > > it doesn't excuse making such a broad statement without qualification. > > We're describing a few sentences down that guests run with EPT > IgnorePAT=1, which is the qualification. > > > > > Just grep in the kernel for a bunch of reasons this is wrong. > > > > Where did this come from? > > Again the logic is very simple: TDX guest code is (mostly) about > replacing KVM code with in kernel code, so we're just doing the same as > KVM. You cannot get any more proven than that. >
I have no problem pointing at KVM as to why the risk is mitigated, but I do have a problem with misrepresenting the scope of the risk.
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